I have already referred (chap. iii.) to the discussions that have taken place over the simian origin of man. All attempts to demonstrate the presence in the human brain of parts that were absent in the simian brain have failed. It is a curious fact that man displays a more marked difference from monkeys in the structure of the reproductive system than in the structure of the brain. There is no _os penis_ in man. This bone, which facilitates intromission, occurs in many vertebrates, not only among rodents and carnivora, which are widely separated from man, but in many monkeys, and most notably in anthropoid apes.[86] For some reason impossible to establish, man has lost this bone. It may be that certain ossifications of most rare occurrence[87] may represent an atavistic inheritance from our remote ancestors. In the male sex the difference between man and the anthropoid ape is the loss of an organ; in the female sex it is the acquisition of an organ. The hymen, the physical indication of virginity, is peculiar to the human race. That organ would serve the purpose of those disputants who make every effort to discover the existence of a structure peculiarly human, far better than the posterior lobe of the brain, or the hippocampus minor. Bischoff[88] has determined its absence in the anthropoid apes, and his result has been confirmed by other observers. Deniker[89] failed to find it either in the fœtal gorilla or in the young gorilla. In the case of the fœtus of the gibbon, he found a slight elevation round the entrance to the vagina “which might be homologised with the hymen,”[90] but which, however, was not the membrane in question. Deniker[91] himself decided that the “membrane was absent in anthropoid apes at all ages.” Weidersheim, in his summary of the organisation of the human body,[92] also sets down the fact that “in monkeys a hymen is not present.” The fact that this structure appears late in the development of the female fœtus bears out the supposition that it has been acquired recently by the race. According to several observers, who agree in this matter, the membrane does not develop until at least the nineteenth week of fœtal life. Although organs very ancient in origin, and now become degenerate rudiments, may be useless, it is to be expected that an organ of recent appearance and still in a progressive condition, would have an important function. Of what utility is this membrane to a woman? Wiedersheim[93] remarks that its function has not been made out. The hymen sometimes plays a large part in family and social relations, and, regarded as the evidence for virginity, has had moral significance bestowed on it. A minute examination of this structure is frequently a part of the judicial procedure in cases of supposed rape and so forth. The destruction of the hymen has led to the death of many hundreds of men and women.